Making Stuff: Stronger

David Pogue tests his mettle against the world's strongest stuff, from steel and Kevlar to bioengineered silk.
Airing August 21, 2013 at 9 pm on PBS
Aired August 21, 2013 on PBS

Originally aired 01.19.11

Program Description

(This program is no longer available for streaming.) What is the strongest material in the world? Is it steel, Kevlar, carbon nanotubes, or something entirely new? NOVA kicks off the four-part series "Making Stuff" with a quest for the world's strongest substances. Host David Pogue takes a look at what defines strength, examining everything from steel cables to mollusk shells to a toucan's beak. Pogue travels from the deck of a U.S. naval aircraft carrier to a demolition derby to the country's top research labs to check in with experts who are re-engineering what nature has given us to create the next generation of strong stuff.

The other programs in the "Making Stuff" series are "Smaller," "Cleaner," and "Smarter."

"Making Stuff" is produced in cooperation with the Materials Research Society (MRS), an international organization of nearly 16,000 materials researchers from academia, industry, and government, and a recognized leader in promoting the advancement of interdisciplinary materials research to improve the quality of life.

Transcript

Making Stuff: Stronger

PBS Airdate: January 19, 2011

DAVID
POGUE (Technology Reporter, New
York Times) Imagine
a world with smart buildings that can ride out any disaster; bacteria that make
gasoline out of thin air; computers that think and place all the world's knowledge
in your pocket; an end to surgery, with tiny devices that can repair cells,
even D.N.A.; gossamer threads, strong enough hold up a bridge; or an elevator
to the stars. These visions of the future are all based in the discoveries of
today, as a new science of materials emerges from the elemental building blocks
of the universe, promising a future in which we can create virtually anything
we want, atom by atom.

Can I have some rock music please?

I'm
David Pogue, and I am on a quest to find the world's most advanced materials.

A
narrow wire that can bring a fighter jet to a dead stop in less than three
seconds...

Welcome to Navy Airlines!

...super strong, but not unbreakable. What new
material might replace it?

A
manmade fiber that can stop a bullet?

Whoa!

Nature is our guide in this quest.

These are your lab assistants?

Inspired by the beak of a tropical bird.

Er, they were all out of parrots.

Or
a lightweight thread spun by spiders, now made from goats' milk.

So this one's skim and this is two percent?

It's stronger than steel!

We're
learning how to make stuff stronger than ever, and it's going to change the
world.

Marc
Meyers (Materials Scientist, University of
California, San Diego): You
should try, too.

DAVID
POGUE: Right now,...

Well it would snap if I had any upper body
strength.

...on NOVA.

Here I am, inside a Navy plane. I'm on a quest to
find the strongest stuff in the world. We're headed for that: the U.S.S. John
C. Stennis. I can't believe it's possible to land on that thing.

But
down on that tiny deck, there's a lifesaving piece of equipment that's supposed
to be strong enough to bring our plane to a dead stop. Man, I hope that thing
holds!

We're going down.

Wow, I really felt that! Now I want to see how it
works.

Welcome to Navy Airlines!

Luckily, I've arrived at the perfect time,
because a dozen new pilots are practicing their landings. That means lots of
attempts to catch that wire.

There are actually four cables across the deck.
They're working on number three right now. So this guy's going to try to catch
number four. That's the ideal one. Let's see if he does it.

The jets land under full power, briefly exerting
hundreds of thousands of pounds of force on a cable that's only an inch and a
half thick. How is it possible that such a thin wire can have so much strength?
I head below deck to get a closer look.

So, I think I understand how these planes land,
because I came in on one of these planes. The plane has a hook underneath, and
then there's this big steel rubber band on the deck that stretches a little
bit, then un-stretches. Am I right?

Scot
Vannorman (United States Navy): No, sir. It looks like that, yes, it does, but that
actual rubber band that you're talking about, the actual wire, comes down here
and actually leaves from here. This is actually the cable that you're going to
see going across that flight deck.

DAVID
POGUE: Every time a plane hits the cable, this powerful hydraulic piston
goes into action. By spooling out wire at just the right speed it counteracts
the momentum to slow the aircraft. The bigger the plane, the harder it pulls.
It's designed to withstand a truly massive load.

SCOT
VANNORMAN: The breaking strength of the
cable is 215,000 pounds.

DAVID
POGUE: That's enough strength to stop four F18s at once. Amazing! And it's
all thanks to a strong material that the Navy trusts above all others.

The entire ship is made of steel.

Don't believe me; tell it to the magnet.

Steel.

Steel provides the structural strength of the
bulkheads, and the decks.

Steel!

And, of course, the all-important arresting
cable.

In
the quest to find strong materials, steel is a great place to start. Our modern
civilization is built on the stuff, but where does it come from?

Thousands
of years ago, ancient people used tools made of stone. That's why it's called
the "Stone Age." But, eventually, they discovered how to extract metals like
copper, tin and iron from rocks. Iron is the main ingredient in steel, but
steel is stronger than iron, because it also contains carbon.

All these materials fill the periodic table of
the elements, a master chart that that lists the basic building blocks of every
material in the world, from the lightest to the heaviest, from the weakest to
the strongest.

The ability withstand pulling forces is called
tensile strength. And steel has it in abundance. But it's not unbreakable.

Each
time a plane hits the wire, the impact takes a toll, with potentially
disastrous results. In 2003, this fighter had nearly come to a complete stop
when the cable suddenly snapped. The plane was lost but the pilot ejected to
safety. Sudden failures like these are rare, because the crew doesn't wait for
the cables to wear out.

So the doubled up cable down here on the pulleys,
you, you replace that how often?

SCOT
VANNORMAN: Every two thousand arrestments.

DAVID
POGUE: And, they're connected to one across the deck up there that has to
be replaced every...

SCOT
VANNORMAN: One hundred and twenty five.

DAVID
POGUE: How come so much more often?

SCOT
VANNORMAN: Well, the one on the
deck—we call it the cross-deck pennant or C.D.P.—the C.D.P. takes
the blunt force of the tailhook: metal-to-metal contact at a hundred and thirty
to a hundred and forty miles per hour, a hundred and twenty-five times.

DAVID
POGUE: It's amazing that they haven't found some material in the whole
world that would last more than a hundred and twenty five landings.

SCOT
VANNORMAN: I don't know of any metal that
can do that yet.

DAVID
POGUE: Steel has incredible tensile strength, but can it be improved?

Can
we make this stuff even stronger?

That's
what Ellwood Steel has tried to do for the last century. They've developed and
produced high-strength steel for everything from aircraft crankshafts in World
War II to high-performance windmill generator shafts and other steel
components. It's all based on the same basic materials, first combined
thousands of years ago.

John
Paules (General Manager, Ellwood
Technologies): The end product,
steel, is a mostly iron—99 percent or so—iron with a little bit of
carbon. First we melt it, and then we refine it. We remove all the impurities
we can to get the properties that we need from the steel.

DAVID
POGUE: At this plant, the raw material is scrap steel, to be recycled.
First it's loaded into an electric furnace for melting.

When
the mix reaches 3,000 degrees Fahrenheit, the liquid metal pours out of the
bottom of the furnace into a ladle. Today, they're making steel for jumbo jet
landing gear, extremely strong and stiff. Besides iron and carbon, the recipe
calls for several additional elements, added in precise quantities. After
cooling, a simple test reveals whether the steel has the right amount of
tensile strength.

John
Paules: When
we pull a piece of steel, we measure how much it stresses. We keep increasing
the load; we watch it stretch, until it eventually breaks.

DAVID
POGUE: The more force it can withstand, the greater the tensile strength.

Where does steel's remarkable strength come from?
In metals like iron, atoms are packed together like sheets of marbles. But when
pushed or pulled, they can slip and slide past each other.

But
steel also contains carbon. The carbon atoms fit in between the iron atoms,
limiting their freedom of movement, making it harder to pull them apart. Steel
makers long ago learned that by adding more carbon, you can increase the
steel's tensile strength, but you give up flexibility, which is something that
the arresting cable needs to wind and unwind. The trick is to find just the
right balance.

John
Paules: Including
steel, there's always been a tradeoff between very high hardness, high strength
and flexibility. Steel has provided a very good combination of high strength
and good flexibility for many applications. That's why it's so widely used.

DAVID
POGUE: Without steel's tensile strength to resist fracture, elevator cables
would snap and bridges would crack in two. That alone makes it an incredibly
valuable strong material. But steel protects us in other ways too. Carmakers
depend on a different kind of strength in steel, which is on display at the
Outlaw Motor Speedway in Muskogee, Oklahoma.

Materials
scientist Mark Eberhart is here to help me understand what makes car bodies
strong. And to do that that, we first have to watch them break.

Mark, you're a prominent scientist, author,
teacher. Why are we at a dirt track in Oklahoma?

Mark
Eberhart (Metallurgist, Author, Why
Things Break): I've been
fascinated with understanding why things break since I was about six years old.
You can go into a lab, and you can do real detailed experiments—they
don't capture the full beauty of why things break. This is the place to come to
really understand what a person means when they say strength.

DAVID
POGUE: We're the Starsky and Hutch of science nerds.

Can
I have some rock music please?

Frankly, I wouldn't mind watching from the
stands, but Mark insists that only by becoming crash test dummies ourselves can
we understand how steel makes car bodies strong.

Mark
Eberhart: Most people don't think of strength
as kind of a monolithic thing, but it really is a combination...

DAVID
POGUE: Hey, what's your hurry pal? Sorry about that.

Mark
Eberhart: It's really a combination of
properties. It's not just one property, the way most people use the word.

DAVID
POGUE: So, really, when we say "strong as steel," it's a little more
complicated than that?

Mark
Eberhart: Oh, absolutely.

DAVID
POGUE: Besides tensile strength, resistance to pulling, there's also
toughness. It's a measure of how much energy a material can absorb without
breaking.

When
a car crashes and the body dents, the steel is absorbing the energy of the
crash. That's toughness.

During
our 100 laps the car took some serious hits. Did the steel demonstrate
toughness?

You know it's not all that much different from
Manhattan at rush hour. Let's check this puppy out.

Danny
Womack (Owner, Outlaw Motor Speedway): We're going to take this car, we're going to send
it into the wall and see what we can tear up.

DAVID
POGUE: Danny locks the steering wheel in place and opens the throttle. Now
it's up to me to do the honors.

In the name of science!

We installed a small camera where the driver
would normally be.

Danny
Womack: Ha ha. That was great.

DAVID
POGUE: The impact was far more intense than anything we experienced during
the race.

Mark, talk us through what's going on here.

Mark
Eberhart: What we can see here is that
we've exhausted a lot of the energy and just crumpling this thing up. I think
we knocked the axle all the way back. Tell me, is that the case, Danny?

Danny
Womack: It looks like it.

Mark
Eberhart: It knocked it all the way back
into the firewall.

Danny
Womack: That deal'll buff right out.

DAVID
POGUE: Would you have lived, Danny?

Danny
Womack: I would have had a heart attack
somewhere between there and here. I don't know.

DAVID
POGUE: Yeah.

Amazingly the car took everything we threw at it.
If the material hadn't been tough, if it had been too brittle, the damage would
have been lethal. But in this case, people would have survived, because the
steel absorbed the energy of the collision. The amount of carbon in the steel
is low enough to let the atoms move just a bit, allowing the steel to bend but
remain intact. That's toughness.

You know, who says science can't be fun? That was
pretty cool.

Steel makes the biggest structures on
Earth possible. And in the future, when buildings reach a mile or more into the
sky and bridges stretch across the sea, steel will be there to support
humanity's dreams, because we haven't come close to exhausting the potential of
this most precious metal. But no material is perfect. Even metals have their
weaknesses.

Consider
the suit of armor. Warriors once wore bronze, iron and steel onto the battlefield.
Sure it was heavy, but it provided good protection, until around the 15th
century. When the gun appeared, heavy armor became a liability.

So,
for hundreds of years, infantry in the world's bloodiest wars went to battle
with little to protect them, because the metal was no match for a bullet. Why?

Luckily,
I have a personal connection to a place where we can see exactly how metals
fail under fire.

This has got to be my favorite spot at M.I.T.,
Strobe Alley, dedicated to the work of my great-uncle Harold Edgerton, a
pioneer in the art of high-speed photography.

I remember, when I was a kid, he was always
showing us pictures of what he was doing. He was smashing light bulbs, shooting
bullets through apples, stuff like that. I thought, "That's the coolest job in
the world."

Our plan today is to fire small, .22 caliber
bullets at several different types of metal. Using a high-speed video camera,
we'll examine the exact point when the bullet hits and we'll examine the type
of hole it creates.

Jim
Bales, who runs Strobe Alley will be our triggerman.

Jim
Bales (Edgerton Center, Massachusetts
Institute of Technology): We've
got two cameras. This one's running at 20,000 f.p.s. This one's down at a mere
4,000 f.p.s.

DAVID
POGUE: Yeah, and, for point of comparison, normal television like this that
you're seeing right now is 30 f.p.s. So these are running a good bit faster.

First up, a piece of steel. It provides about as
much protection as a 15th century breastplate.

Jim
Bales: Three,
two, one.

DAVID
POGUE: Even this small caliber bullet easily penetrates, leaving a jagged
hole.

Looks like someone has ripped a hole through a
piece of paper.

To provide enough protection for a soldier's
torso, this steel would have to be 10 times thicker. It would weigh an unwieldy
100 pounds.

What
about a lighter weight material, like aluminum?

We
see it mostly as flimsy rolls of foil but some forms of aluminum are just as
strong as steel and are widely used in aircraft construction. Could aluminum
serve as armor?

Lo and behold, there's a hole in the metal.
Metallurgist, Mark Eberhart:

Mark
Eberhart: This is beautiful. The energy of
the bullet or much of the energy went into folding that metal back.

DAVID
POGUE: The aluminum shows even more tearing at the point of impact. Pieces
of metal light enough to be worn as armor aren't tough enough to stand up to
the focused energy of a gunshot. When a bullet strikes the surface, the energy
of impact is transferred to the metal in the form of heat, which causes the
atoms to slide past each other.

Because
the energy is focused on such a small area, the movement can be severe, causing
cracks to form. If the material is thin enough, the bullet tears right through,
like a hot knife through butter. So wearing a full metal jacket into combat is
not a wise idea.

But if guns made personal armor obsolete, what
are these guys wearing? It looks like cloth, but it's stronger than steel, and
it's become standard equipment for soldiers, swat teams and bomb disposal
squads.

I'm
talking about Kevlar. When this synthetic fiber is woven into a fabric, Kevlar
is strong enough to stop a bullet, or a blade, or even, with a few chemical
changes,...

Ha ha.

...a fire.

Oh, it's hot, although, not as hot as he is.

Tucker
Norton (Ballistics Scientist, Dupont):
David, what you're about to see here are all the examples that we've got of
Kevlar.

DAVID
POGUE: This is Tucker Norton, ballistics expert and my tour guide here at
DuPont, the company that invented the stuff.

Tucker
Norton: Over here, we have some examples
of vests where Kevlar is being used.

DAVID
POGUE: Can I try one of these on?

Tucker
Norton: Absolutely.

DAVID
POGUE: Okay, I'm not here to show off the spring collection but to
understand what makes this stuff so strong.

Kevlar,
so important to American soldiers today, has its roots in a time when the
entire United States was in peril. In the early '30s, the Japanese empire
seized control of the world's silk supply, a material used to make parachutes
and flak jackets. A frantic search began for a manmade replacement. Then in
1935, Wallace Carothers, a brilliant chemist at DuPont, created nylon, the
first fiber made in a test tube, not in nature.

His
breakthrough ushered in the modern age of synthetics. Then, in the 1960s, Stephanie
Kwolek, a chemist, also at DuPont, created Kevlar. It remains the strongest
synthetic fiber ever produced.

I
know Kevlar can hold up in the most extreme punishment, but I want to see it up
close. Our target: a block of clay designed to simulate the human torso.

It's
protected by several layers of Kevlar. On the other end: the weapon, or rather
the "bullet delivery device."

This is the gun?

Tucker
Norton: This is the gun.

DAVID
POGUE: Oh, I was expecting a "gun."

Tucker
Norton: No, none of that.

DAVID
POGUE: Oh, you're kidding?

What's going to happen? Someone's going to pull the trigger and... is there a
trigger?

Tucker
Norton: So the trigger is located outside
of here. We don't actually do anything firing here, while we're inside.

DAVID
POGUE: You guys are these giant safety wusses.

Tucker
Norton: Now, here's where we go to fire.

DAVID
POGUE: I feel like the President, failsafe.

Okay,
ready, aim, fire!

Tucker
Norton: You did it.

DAVID
POGUE: Geez, I am so good.

Time to inspect the damage. Even with Kevlar, the
simulated chest takes a beating.

Whoa! This is...this would have been my chest?

Turns out it looks worse than it is.

Tucker
Norton: Unlike the human body, this clay
will hold its position. The human body will respond and go back to normal.

DAVID
POGUE: So, on a human, this would just be a really nasty bruise?

Tucker
Norton: Yes.

DAVID
POGUE: And maybe a broken rib?

Tucker
Norton: That's right.

DAVID
POGUE: Gotcha.

Tucker
Norton: That's right.

DAVID
POGUE: Still, ouch! But where's the bullet?

In
fact, it's in the bag.

Tucker
Norton: The bullet's still in here.

DAVID
POGUE: Oh, my gosh. Can we see it?

Tucker
Norton: Absolutely. So we have many, many
layers, of course. The first one, second one, and usually about the third layer
is where it gets stopped. And there it is. There's the bullet.

DAVID
POGUE: Oh, my gosh.

It took just four layers of Kevlar, each less
than a millimeter thick, to stop the bullet. The seven other sheets kept that
hole from getting any deeper.

Tucker
Norton: And as deep as any type of trauma
might look, it's much better than that bullet going all the way through you.

DAVID
POGUE: Right, I guess I could agree with that.

Kevlar is clearly some tough stuff.

Whoa!

But how does it work?

Tucker
Norton: If you were to zoom down at about
100-million times...

DAVID
POGUE: Well, we have a really nice camera, can you zoom down 100-million
times?

Kevlar is a polymer, a long repeating chain of
atoms, in this case, carbon, hydrogen, oxygen and nitrogen. Each chain is like
a stiff piece of spaghetti. Gathered into bundles, the stiff chains create a
thread-like fiber that has a hard surface, extremely high tensile strength and
enough toughness to absorb the impact of a bullet.

Stopping
a round is impressive, but there are other threats out there. How does Kevlar
stand up to a knife or an ice pick?

Don't
try this at home.

I'm not going to pay a lot for this muffler!

I said, "Caesar, on the side."

Twenty cents a text message? Are you nuts?

That's amazing. How can it do that?

Tucker
Norton: Well, it does it because of the
tight weave and because of the strength and durability of Kevlar. The tight
weave prevents the spike from getting all the way through, from working its way
through. And the strength of that Kevlar actually helps blunt that tip and
maybe even bend that tip if you are strong enough.

DAVID
POGUE: Since it was invented, Kevlar has been used in all kinds of
products, from tires to parachutes and even cables. And that gives me an idea.

Tucker, I've got this friend. Um he's got a fleet
of nuclear aircraft carriers and, they have these steel cables, a lot like
this, that are designed to stop aircraft that are landing, 130 or 150 miles an
hour. How does the strength of one of these cables compare with a steel cable?

Tucker
Norton: Well, we'd expect the strength of
this, the tensile strength, to be actually equal or better than something like
the steel cable.

DAVID
POGUE: And, it's lighter and it's less dangerous if it snaps?

Tucker
Norton: That's right.

DAVID
POGUE: Tucker doesn't think that anyone has ever tested Kevlar arresting
cables, but I think I may be on to something.

This, this could be a sales opportunity for you.

Tucker
Norton: We appreciate that, thank you very
much, David.

DAVID
POGUE: I'll look for my commission.

With its tensile strength greater than steel,
extreme flexibility and heat resistance, in a package that weighs one-fifth as
much as steel, Kevlar could, one day, be a replacement for steel cables. But
already there may be other, stronger alternatives.

Scientists
like Ray Baughman, at the University of Texas, are exploring the remarkable
properties of a brand new material.

I'm
talking about the carbon nanotube.

Ray
Baughman (Chemist, University of Texas at
Dallas, NanoTech Institute):
Dave, this is one type of carbon nanotube.

DAVID
POGUE: This is what it's all about, right here?

Ray
Baughman: This is what it's all about.

DAVID
POGUE: You know, I had a hunch they'd be like this. I just thought they'd
be smaller.

I'm right. They're about a billion times smaller.
Nanotubes are made of carbon atoms arranged in a rolled up, chicken-wire like
structure. Besides nanotubes there are other forms of pure carbon, like diamond
and graphite, the stuff of pencil lead. Nanotubes get their strength from the
extremely strong bonds between carbon atoms.

Ray
Baughman: These carbon nanotubes can have
spectacular mechanical properties, spectacular strength and very high
toughness.

DAVID
POGUE: And you make them here in this very lab?

Ray
Baughman: Yes, we do.

DAVID
POGUE: Ah, so this is where it all happens.

Ray
Baughman: This is where the process
begins.

DAVID
POGUE: And guess what? It's not even that difficult. Here's all you need:

One,
a smooth surface with a thin layer of catalyst, a chemical that helps
jump-start the tubes; two, a special mix of gases, full of carbon atoms, and
three, this furnace, which, by the way, is really, really hot.

DAVID
POGUE: Oh, man, that is blasting heat. Oh, I see the little black wafer in
there. That's it?

Mírcio
Dias Lima: Yup.

DAVID
POGUE: That's nanotubes?

Mírcio
Dias Lima: Those are, yes, exactly.

DAVID
POGUE: Wow. That is very cool, baking away in there. Wow, it's like a
nuclear tanning bed.

After just a few hours, the wafer is covered with
a thick, black fuzz.

So, it looks just like a piece of black velvet.

So,
if I were to really look in close to that, what would I see? What's it really look
like under the microscope?

Ray
Baughman: Well, we call this array of
carbon nanotubes a nanotube "forest."

DAVID
POGUE: The name is apt. Each nanotube looks like a tall and thin bamboo
tree: hollow inside, so thin that if you could scale one up until it was one
inch wide at the base, the top of it would reach two miles into the sky. Now,
picture nanotubes by the billions, all standing shoulder to shoulder and you
have one of Ray's nanotube forests.

Ray
Baughman: There are, in fact, there are
about 200 billion of carbon nanotubes in that area.

DAVID
POGUE: Hold on one second, I'm going to count them.

Actually, I shouldn't be touching these.
Scientists don't yet know if they are toxic.

Even
so, there is already a rapidly-growing market for nanotubes particles as
strength additives for tennis rackets, bicycle frames, even high-end car
bumpers. Many products already incorporate carbon fibers, which are part
carbon, part plastic. But nanotubes have greater tensile strength and
toughness. Ray has set his sights on making super-strong materials that are 100
percent pure nanotube, made from his nanotube forests.

Ray
Baughman: These aren't just ordinary
carbon nanotube forests. They are nanotube forests that have a very special
type of connectivity between nanotubes.

When
we pull out one nanotube, that nanotube pulls out its neighbors, who pulls out
other neighbors, to self-assemble a yarn or a sheet.

Chi
Lewis Azad (University of Texas at Dallas,
NanoTech Institute): Would you
like to try?

DAVID
POGUE: This I recognize.

First, we start with a forest on a wafer.

Chi
Lewis Azad: You see, you can just grab on
to this little orange tab. Now, don't make it too high of an angle, and make
sure it doesn't touch the edge, and just pull out.

DAVID
POGUE: Fast or slow?

Chi
Lewis Azad: Whichever you feel comfortable
with.

DAVID
POGUE: Oh, dude!

As I pull on this little tab, nanotubes are
coming off of the wafer, hooking other nanotubes and pulling them off of the
slide.

Chi
Lewis Azad: Try faster.

DAVID
POGUE: I'm so good at this.

Chi
Lewis Azad: At too high of an angle it
will—as this is now
—it will start to break off from the forest.

DAVID
POGUE: It's like coming out forever. I'll see you at the Texas county line!

It's
still going, it's still going.

Chi
Lewis Azad: It's still...There, it broke.

And, what's even neater, I can show you right here, I can even do a little
twist.

DAVID
POGUE: Oh, you're making...

Chi
Lewis Azad: Make it into a yarn right
here.

DAVID
POGUE: Insta-yarn.

Chi
Lewis Azad: Look at that.

DAVID
POGUE: Wow.

Chi
Lewis Azad: It's about 1/100th of a human
hair.

DAVID
POGUE: Oh, my gosh. It is like steel. I'm pulling really hard. You probably
can't even see that. In fact, look at this. It's so fine, you can't even see
it.

Oh,
that helps.

Chi
Lewis Azad: Uh hunh. Keep twisting, keep
twisting.

DAVID
POGUE: Keep twisting? Okay.

It's amazing!

Chi
Lewis Azad: It's stronger than steel.

DAVID
POGUE: Stronger than steel? So why then, don't you take a bunch of these,
twist them together, and make this super-cable that would be like bridge
suspension cables and aircraft carrier cables?

Chi
Lewis Azad: Can you imagine spinning a
bunch of these all day long, to make into a rope that's a foot in diameter?

DAVID
POGUE: Okay, so go the other way. Make the aircraft carriers really, really
small.

Chi does have a point, for now. But in the
future, materials we make may be strong, light and cheap enough to build incredible
structures: a bridge across an ocean, suspended by cables made of fibers like
Kevlar or nanotubes; a geodesic dome over an entire city, its structure made of
carbon.

And
in the future, we may not merely make these materials, we may grow them. That's
what Mother Nature has been doing for hundreds of millions of years,
engineering strength into the bodies of animals, one atom at a time.

Meet Marc Meyers. He's been fascinated by
nature's engineering tricks ever since a boyhood encounter in a Brazilian
forest.

Marc
Meyers: My
father was hunting, and I saw this entire toucan skeleton. Then I picked up the
beak and I was amazed at how light it was, and how strong it was.

DAVID
POGUE: The memory stayed with him for 30 years, until he happened to stumble
across, of all things, a toucan farm. There, he made a startling discovery. In
the toucan's amazing beak, nature has constructed a large, lightweight and
amazingly tough structure. He wanted to know how.

I'd
like to know why. Conservationist Joan Embery is on hand to explain.

What is the point of this huge beak? I mean, it
does look a little ridiculous.

Joan
Embery (Embery Institute for Wildlife
Conservation): Well, they're
primarily a fruit-eater, and that extends their reach. They use it as a screwdriver.
They use it to find food. Also works defensively as a dagger. The edges are
serrated.

DAVID
POGUE: You tell me that now, when the thing is like six inches from my eye?

Joan
Embery: That's
why you're holding the tame toucan.

DAVID
POGUE: Oh!

When Marc analyzed the beak of the dead bird, he
found that it was made out of two different materials, neither one of which is
strong.

On
the outside is the shell. It's
like bendable plastic, it feels like a, like a fingernail.

Marc
Meyers: If
the beak was just like this, it would flex. It would, it couldn't grab
anything.

DAVID
POGUE: The inside of the shell is filled with bone, but bone that's so full
of air pockets it's as weak as Styrofoam.

Marc
Meyers: See
how it can break easy? You see?

DAVID
POGUE: Right. Nothing.

Marc
Meyers: And,
oh, you should try, too.

DAVID
POGUE: Yeah, exactly. Well, it's, it's foam, so it snaps. Well it, it would
snap if I had any upper body strength.

The thin shell and the foamy bone, neither one is
tough , but when combined...

Marc
Meyers: You
can see that this is the foam.

DAVID
POGUE: Mm-hmm.

Marc
Meyers: And
then we have the shell.

DAVID
POGUE: Right. Each by itself...

Marc
Meyers: ...is
weak.

DAVID
POGUE: ...is
weak.

Marc
Meyers: I
can show...yeah. If you pull out...it can bend this, here, very easily. Here, you
see?

DAVID
POGUE: Yeah.

Marc
Meyers: And, uh...

DAVID
POGUE: And this I could snap, if it weren't an important teaching tool for
you?

Marc
Meyers: That's
right.

DAVID
POGUE: Yeah. And if you combine them...

Marc
Meyers: And
now, if you take and try to bend these two together, see?

DAVID
POGUE: Oh, wow.

Marc
Meyers: Yeah.

DAVID
POGUE: It's like super-lightweight concrete. It feels...

Marc
Meyers: Right.

DAVID
POGUE: It feels like nothing.

Marc
Meyers: It
is strong, and it is, uh, it is very lightweight.

DAVID
POGUE: Marc was amazed that evolution had solved such a difficult
engineering problem. So he began looking for other examples of animal
engineering, which soon led him from the jungle to the beach.

This is your lab? You work in a wetsuit on a
table by the ocean?

Marc
Meyers: For
today it is. I've been, ah, studying, actually, these shells, the abalone, for
some years, because they are very, very strong.

DAVID
POGUE: The abalone has evolved to have a very tough shell which protects it
from the pounding surf and from predators like sea otters.

What is this shell made of? It's not...you're
saying it's not like other shells?

Marc
Meyers: It's
calcium carbonate, which is the same as chalk.

DAVID
POGUE: Chalk? Huh.

Marc
Meyers: But
it's much, much stronger than chalk.

DAVID
POGUE: Yeah, chalk is not especially strong. I notice, by pure coincidence,
there's a piece of chalk right here. And I don't think of chalk as
sea-otter-proof. I mean, it just crumbles.

Marc
Meyers: It
crumbles.

DAVID
POGUE: The fact that it pulls apart so easily shows that chalk has very
little tensile strength or toughness. But that's not the end of the story.

Marc
tells me not to be fooled by chalk's apparent weakness, because it's actually a
very strong material.

I was never any good at dominos.

Marc
Meyers: Now,
you said that this is weak, right?

DAVID
POGUE: Yeah.

Marc
Meyers: You broke it with your, uh...

DAVID
POGUE: My bare hands.

Marc
Meyers: Yeah.
And now I'll show to you that you can put your entire weight here, if you step
carefully, here.

DAVID
POGUE: Use you as a ladder?

Marc
Meyers: Yeah.

DAVID
POGUE: Alright.

Marc
Meyers: Put
more in the middle.

DAVID
POGUE: More in the middle?

Marc
Meyers: Yeah,
yeah.

DAVID
POGUE: You've got to be kidding me. This is going to shatter 'em like
glass.

Marc
Meyers: See?

DAVID
POGUE: Wow! One-hundred-eighty-five pounds of pure muscle!

Marc
Meyers: Yes.

DAVID
POGUE: Look at that!

What's going on here?

Chalk
can withstand tremendous pressure. It's called compressive strength, and it's a
property of ceramics, the stuff of pottery, bricks and the cement in concrete.
But ceramics also have a weakness.

Bend
them, drop them, shoot them or even take a hammer to them...

For your $25 pledge, we'll send you this handsome
coffee mug.

...and they shatter.

As with other materials, the strength or weakness
of ceramics is determined by how their atoms bind together. Chalk is made of
calcium, carbon and oxygen atoms, which are bonded together tightly, with no
wiggle room. They can't slide past each other. That lets them to stand up to
tremendous pressure. But if a small crack manages to open a space between the
atoms, it can quickly spread. That's why materials like chalk, even though they
have high compressive strength, often seem fragile.

Take glass, another fragile material. Marc
insists that it also has high compressive strength, even more than chalk.
Frankly, that seems hard to believe.

Okay, here we go. I'm going to wind up with an
ankle full of glass.

Oh, my gosh! The chalk is one thing, but these little skinny wineglass stems
are something else entirely.

Marc
Meyers: Now
are you willing to try it with three or two?

DAVID
POGUE: No.

Three
glasses! Three glasses! Where's the Cirque de Soleil agent when you need him?

Marc
Meyers: That's
amazing! You did it!

DAVID
POGUE: Alright, Marc, explain this in science terms, quick!

Marc
Meyers: Ceramics
and glasses, when we compress them, they're very, very strong, stronger than
metals.

DAVID
POGUE: Okay, shall we try one?

Marc
Meyers: Yes
go for it!

DAVID
POGUE: Let's
do one glass. One glass, people!

Marc
Meyers: Let's
do it!

DAVID
POGUE: Whoa! Whoa! Oh, my god! I can't believe it! How is this possible?

While that is impressive, the abalone shell blows
glass and chalk out of the water, so to speak.

Like
the toucan shell, it combines two materials to make its fortress of strength
and protection. Its shell is 95 percent calcium, carbon and oxygen, just like
the chalk, but it doesn't have the same brittle weakness. It's not fragile.

You're saying this is 95 percent the same as
this, but this...

Marc
Meyers: Yeah,
but, try to break this.

DAVID
POGUE: But this one...really?

Marc
Meyers: Yeah,
go ahead.

DAVID
POGUE: This would cost a fortune at the gift shop.

Marc
Meyers: No,
yeah, go ahead. I dare you.

DAVID
POGUE: Okay, if I were a sea otter, I would be a terrible failure. It's
completely... Nope.

The shell demonstrates both compressive strength
and toughness, the ability to absorb energy without breaking, thanks to the way
that the abalone has engineered its protective cover on a microscopic scale.

As
it constructs its shell, the abalone gathers calcium, carbon and oxygen from
the environment to build rows of tiny, hexagonal plates. Each plate is brittle,
but between the layers, the abalone inserts a protein, a long biological chain.
That small addition acts like a shock absorber between the plates. The
resulting shell is far less brittle, much tougher and more crack-resistant than
simple chalk.

As
we learn to apply the lessons of microscopic structure, engineers may one day
build pressure-resistant ceramics and glass from the atom up, beautiful
buildings of sculpted concrete that will never crack and will last 1,000 years,
or a deep sea city with a spectacular view.

But
when it comes to strong, light and flexible materials, built atom by atom,
another natural material may hold the key.

It's
not new. In fact, it's been around for hundreds of millions of years: spider
silk. Spider silk has been shown to have more tensile strength than steel and
Kevlar. It can stretch to 140 percent of its length without breaking and
remains flexible, even in extreme cold. It's also so lightweight that a mere
pound of the stuff could form a single strand long enough to stretch around the
equator.

But
could we harvest enough to put it to use?

I
paid a visit to the American Museum of Natural History, in New York, where I
met Nicholas Godley.

This is it? This is your baby?

Nicholas
Godley (Fashion Designer): This is the big one.

DAVID
POGUE: ...who enlisted the help of more than a million spiders to make this
breathtaking piece of fabric.

Nicholas
Godley: It's the largest known textile and
sample of piece of spider silk in the world.

DAVID
POGUE: To truly appreciate this remarkable material, you have to feel it.

The
main piece is so valuable it's off-limits, even to its creator, but Nicholas
has brought a smaller sample.

It feels really, really, really soft, like animal
wool or something.

Nicholas
Godley: I challenge you to break off this
piece.

DAVID
POGUE: I'm going to break before it does. Okay, it does not...it's like
pulling a strand of steel. Wow!

Nicholas
Godley: It's very difficult to do this on
a commercial scale. It took a million-sixty-three-thousand spiders, roughly, to
make...

DAVID
POGUE: Geez!

Nicholas
Godley: It takes about 20 minutes for each
spider, and they produce about 400 yards of thread.

DAVID
POGUE: Each thread was pulled, by hand, from a spider's spinneret.

It
took four years and millions of strands to weave this 11 foot-long masterpiece.
Its rarity is a testament to the sheer difficulty in harvesting this material.
But that may soon change, thanks to this guy.

Randy
Lewis (Molecular Biologist, University of
Wyoming): So here's where we
keep our spiders. Um, we have special little cages for them, in this room.

DAVID
POGUE: Spider central, huh? Whoa, not funny. Not funny!

Randy
Lewis: You're
now an official Spiderman affiliate!

DAVID
POGUE: This is Randy Lewis, a biologist at the University of Wyoming, who's
stuck on spider silk.

Wow.

Randy
Lewis: This
is a golden orb weaver.

DAVID
POGUE: Golden orb weaver?

RANDY
LEWIS: Just cup
your hand and get behind her.

DAVID
POGUE: Why is she making a web right now?

RANDY
LEWIS: Because she
wants to make sure if she falls, she catches herself.

DAVID
POGUE: Oh, so she's constantly spinning out that dragline.

RANDY
LEWIS: Whenever
they move, they leave the dragline behind. That's kind of where it got its
name.

DAVID
POGUE: Randy has been fascinated by the amazing properties of dragline silk
for fifteen years.

And
he knows all too well the difficulty of extracting silk from spiders. So he set
out find a way to mass produce the stuff, in hopes of revolutionizing the world
of strong materials.

Wyoming
is ranch country, so when Randy began to consider how to solve the problem, his
thoughts turned to livestock. He figured maybe he could combine a little
old-fashioned animal husbandry with the emerging science of genetic
engineering.

Now,
thanks to Randy, these goats have just a little bit of spider in them.

"Transgenic," that's the word for what these
goats are.

RANDY
LEWIS: Right. It
means that they have a gene from another organism that's been put into their
chromosomes.

DAVID
POGUE: Genes are sections of D.N.A. that contain the encoded instructions
for making proteins.

Scientists
identified the two genes in spider D.N.A. that make silk. They copied one of
the genes and spliced it into the D.N.A. of goats so that they would make
spider silk protein in their milk.

I'm a little worried about what we're going to
find in here—eight-legged goats, giant dripping webs?

Randy
Lewis: You won't be able to tell the normal goats from the
transgenic goats, 'cause they're all exactly the same.

DAVID
POGUE: Aww,
I had a dog like you once.

It's impossible, just by looking, to tell these
goats from their non-spidey brethren, but, scientifically, they're very
valuable.

Yeah, you're special. You've been genetically
modified. How does it feel to be genetically modified? Huh?

Only 50 percent of Randy's goats will inherit the
necessary gene, and the females that are born with it will go on to produce
spider silk protein in their milk.

And
that's what I've come all this way to see for myself.

Can I... try it?

Randy
Lewis: You're
certainly welcome to. We normally use the electric, just because it's a whole
lot faster, but, um, you're welcome to

DAVID
POGUE: Faster? But you've never seen me milk a goat.

Randy
Lewis: All
right, well, you're about to find out here.

DAVID
POGUE: So this one's skim and this is two percent?

RANDY
LEWIS: Well, in
this case, they're both spider silk. You can choose either one you want.

DAVID
POGUE: Okay, so I just grab and tug, just like...?

Randy
Lewis: Right,
just squeeze down, and just use your fingers, and just...

DAVID
POGUE: Wow.

What
percent of this milk is spider-silk stuff?

RANDY
LEWIS: For most of
these, it's relatively low, so we're talking about... um... maybe one to two
percent.

DAVID
POGUE: Gives two percent milk a whole new meaning.

Randy
Lewis: That's
right, two percent, um yeah. We'd love, we'd love to see 10 percent, but we'll
take two percent, at this point in time.

DAVID
POGUE: Next begins the painstaking process of coaxing the silk protein out
of the milk.

Randy
Lewis: So
we take the milk that we collected out at the farm, we pump that onto this
column, which has a whole bunch of very small tubes in it.

DAVID
POGUE: Right.

Randy
Lewis: Tubes have holes in it, so that the spider silk
protein and the milk proteins come out of the tubes, and it keeps the fat
inside.

RANDY
LEWIS: Um, from
our best goats that would be about a quart of milk.

DAVID
POGUE: Wow. And then, what...how much silk can you get out of this?

Randy
Lewis: We
can get at least two to three meters.

DAVID
POGUE: Wow! Alright let's have a look.

The final step is the most delicate. Randy's team
takes the protein liquid and slowly injects it into an alcohol bath, which
causes the liquid protein to solidify into a strand of actual spider silk.

So this is it? So this is your manmade spider
silk?

Randy
Lewis: This
is manmade spider silk.

DAVID
POGUE: Now, to prove its mettle, Randy loads the strand into a machine that
measures tensile strength.

Randy
Lewis: Look, you can start to see it moving.

DAVID
POGUE: It
is, it's straightening out.

The silk stretches as it resists being pulled until...

It just broke. I'm sorry, Randy.

Randy
Lewis: It
just broke.

DAVID
POGUE: But there's nothing to be sorry about. A computer measures the force
it takes to break the sample, telling them its tensile strength. Remember, the
tensile strength of steel, its resistance to being pulled, is what kept my
plane from plunging into the ocean.

The
tensile strength of spider silk appears to be greater than steel or even
Kevlar. Not as strong as carbon nanotubes, but more flexible, easier to make in
long strands, and certainly not toxic.

Randy
Lewis: We
are stronger than Kevlar, we're stronger than steel, but we're not stronger
than the natural silk.

DAVID
POGUE: The spider silk protein demonstrates nature's ingenuity. Its
ingenious structure is comprised of three distinct sections.

Randy
compares one of those sections to children's building blocks.

Randy
Lewis: If
you look at a molecular model, what you see is that they have little pins and
little holes, just like LEGOs. So if you take and put them together and stack
them up, like this, and try to pull them apart...

DAVID
POGUE: These are, these are the proteins here?

RANDY
LEWIS: These are
the proteins. And that's part of the protein we try to pull apart. It doesn't
pull apart.

DAVID
POGUE: Okay, so if I'm pulling this way and this way, and this is the
dragline, and it's not coming apart...

Randy
Lewis: Yeah, that's right. So that's one part of the
dragline.

DAVID
POGUE: Proteins: good for you. Okay.

Randy
Lewis: So
four hundred million years, spiders've been playing with LEGOs.

DAVID
POGUE: The second section of the protein is stretchy.

Randy
Lewis: For
elasticity, they have something that literally looks like a molecular spring.
When you pull on the ends...

DAVID
POGUE: Right.

RANDY
LEWIS: ...it
stretches.

DAVID
POGUE: Okay,
so...

Randy
Lewis: And, and, and that the elasticity...

DAVID
POGUE: This would be a different protein?

RANDY
LEWIS: No, it's
the same protein. It has different parts.

DAVID
POGUE: Okay.

Randy
Lewis: So
we have, in the same protein, we have LEGOs, ...

DAVID
POGUE: Right.

Randy
Lewis: ...we
have springs,...

DAVID
POGUE: Okay.

Randy
Lewis: And
then, in order to put them together, we have zippers.

Zippers
hold things together very well, but they have some flexibility, so you have a
way of being able to put this together. With a spring, might be too tight to do
that, so you put a zipper in between: now you have dragline silk.

DAVID
POGUE: These basic building blocks repeat over and over again, trillions of
them in each strand of silk.

The
complex structure is evolution's way of enhancing the strength of the common
raw materials found everywhere in nature.

Before
I leave, Randy suggests one last experiment for us would-be Spidermen.

You getting anything?

RANDY
LEWIS: I don't
feel a thing.

DAVID
POGUE: Nothing.

So it seems that the next chapter in the story of
strong materials is already upon us.

For thousands of years, we've experimented with
our planet's raw materials to make metals and ceramics. Then, through
chemistry, we created synthetics and built materials atom by atom. Now
scientists are learning to combine the engineering tricks found in the living
world with the incredible strength of our own inventions. With these new tools
and materials, there's no telling what we'll be able to accomplish, once again
propelling human civilization across a new frontier, as has happened again and
again, over millennia, every time we learn more about making stuff stronger.

Education and Outreach Resources

Click here for a collection of materials science resources, activities and demonstrations developed in conjunction with Making Stuff: Stronger, Smaller, Cleaner, Smarter. These outreach materials will enable educators and scientists to engage audiences in formal and informal settings and encourage appreciation and better understanding of our material world in the young and old alike.

Major funding for "Making Stuff" is provided by the National Science Foundation.

This material is based upon work supported by the National Science Foundation under Grant No. ESI-0610307. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Additional funding for "Making Stuff" is provided by the Department of Energy.

This material is based upon work supported by the Department of Energy under Award Number DE-SC0004787.
Disclaimer: This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendations, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

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